As communication technologies have been advanced, various types of units, including not only personal computers but also PDAs (personal digital assistants) and television receivers, have been able to be connected to a network these days.
Various systems have been proposed such as that in which images reproduced by a personal computer are sent to a television, receiver through a home network and viewed by using the television receiver.
Although connecting each unit to a network has been gradually made possible with a simple setting, however, it is necessary to set the address of a mating unit and others to execute communication with the unit on all such occasions, and this setting is troublesome.
To display an image reproduced by a personal computer on a television receiver, for example, the user needs to operate the personal computer to specify the address of the television receiver and others.
When many units are connected to a network, it is difficult to check that which unit is connected to which unit. In consideration of the current situation, in which it is expected that structuring networks by radio communication, such as a radio LAN (local area network) and Bluetooth™, has been further spread, there is the possibility that the issue will become further serious in which units connected to each other are not known.